OS MasterMap - AbsoluteAstronomy.com

OS MasterMap® is Ordnance Survey

Ordnance Survey

Ordnance Survey , an executive agency and non-ministerial government department of the Government of the United Kingdom, is the national mapping agency for Great Britain, producing maps of Great Britain , and one of the world's largest producers of maps.The name reflects its creation together with...

's flagship digital product, launched in November 2001. It is a database

Database

A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...

that records every fixed feature of Great Britain

Great Britain

Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

larger than a few metres in one continuous digital map

Map

A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes....

. Every feature is given a unique TOID

TOID

A TOID is a unique reference identifier assigned by the Ordnance Survey to identify every feature in Great Britain. The identifier consists of two parts, a prefix ‘osgb’ and a unique identifier that is 13-16 digits long...

(TOpographical IDentifier), a simple identifier that includes no semantic information. Typically each TOID is associated with a polygon that represents the area on the ground that the feature covers, in National Grid

British national grid reference system

The Ordnance Survey National Grid reference system is a system of geographic grid references used in Great Britain, different from using latitude and longitude....

coordinates. OS MasterMap is offered in themed "layers", for example a road layer and a building layer, each linked to a number of TOIDs. Pricing of licenses to OS MasterMap data depends on: the total area

Area

Area is a quantity that expresses the extent of a two-dimensional surface or shape in the plane. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat...

requested, the layers licensed, the number of TOIDs in the layers, the period in years of the data usage.

OS MasterMap can be used to generate maps for a vast array of purposes. Although the scale on a digital map is much more flexible than a paper map, one can print out maps from OS MasterMap data with detail equivalent to a traditional 1:1250 paper map.

Ordnance Survey claims that OS MasterMap data is never more than six months out of date, thanks to continuous review. The scale and detail of this mapping project is so far unique. Around 440 million TOIDs have so far been assigned, and the database stands at 600 gigabytes in size. OS MasterMap is currently (August 2005) at version 6.

Ordnance Survey is encouraging users of its old Land-Line

Land-line

In the UK Land-Line is a comprehensive dataset, provided by Ordnance Survey, depicting man-made and natural features ranging from houses, factories, roads and rivers to marshland and administrative boundaries. Land-Line is a vector format ....

data to migrate to OS MasterMap.

Topography Layer

The OS MasterMap Topography Layer represents topography at a scale of 1:1250. It is further subdivided into a number of themes: land area classifications' buildings, roads, tracks and paths, rail, water, terrain and height, heritage and antiquities, structures; and administrative boundaries http://www.ordnancesurvey.co.uk/oswebsite/products/os-mastermap/topography-layer/index.html.

Integrated Transport Network

OS MasterMap® Integrated Transport Network™ (ITN) Layer maps Great Britain’s road network – from motorways to pedestrian streets. It contains attributes to enable the routing of vehicles, taking into account the limitations of the road network.
http://www.ordnancesurvey.co.uk/oswebsite/products/os-mastermap/itn-layer/index.html

OS MasterMap Address Layer 2

OS MasterMap Address Layer 2 is a dataset that describes the location of addresses. It is designed to be used as a means of geo-referencing addresses and attempts to improve on Address Point. Address Layer is a part of the National Spatial Address Infrastructure

National Spatial Address Infrastructure

The National Spatial Address Infrastructure was a database proposed by the UK Office of the Deputy Prime Minister on 26 May 2005 with the intention of creating a single repository of addresses for the UK...

and contains National Land and Property Gazetteer

National Land and Property Gazetteer

The National Land and Property Gazetteer is an initiative in the United Kingdom to provide a definitive and consistent address — see address — infrastructure for the whole of the UK...

attributes that classify properties. It is currently at the centre of a dispute between Ordnance Survey and Intelligent Addressing, the custodian of the National Land and Property Gazetteer dataset http://technology.guardian.co.uk/weekly/story/0,,2070577,00.html.
http://www.ordnancesurvey.co.uk/oswebsite/products/os-mastermap/address-layer-2/index.html

Imagery Layer

The Imagery layer is a national collection of 25cm resolution aerial photos.
http://www.ordnancesurvey.co.uk/oswebsite/products/os-mastermap/imagery-layer/index.html

Delivery of the data

OS MasterMap data is in GML

Geography Markup Language

The Geography Markup Language is the XML grammar defined by the Open Geospatial Consortium to express geographical features. GML serves as a modeling language for geographic systems as well as an open interchange format for geographic transactions on the Internet...

format. It is usually delivered as files compressed with gzip

Gzip

Gzip is any of several software applications used for file compression and decompression. The term usually refers to the GNU Project's implementation, "gzip" standing for GNU zip. It is based on the DEFLATE algorithm, which is a combination of Lempel-Ziv and Huffman coding...

(giving them an extension 'gz').

Recently, Ordnance Survey has been trialing delivery of OS MasterMap data using WFS

Web Feature Service

The Open Geospatial Consortium Web Feature Service Interface Standard provides an interface allowing requests for geographical features across the web using platform-independent calls...

and WMS, in accordance with the Open Geospatial Consortium. This trial may even end up with automatic updates using WFS-T.

Custodianship of the data

Although branded like a commercial product, OS MasterMap is in fact the UK’s most complete, accurate and up-to-date geographic record. By moving to purely digital media for mapping, Ordnance Survey brings upon itself the responsibility of being the sole mandatory custodian of Great Britain's official maps. Previously, by virtue of being a publication on paper, a copy of every edition of every paper map published by Ordnance Survey would have been deposited, by law, with each of the six legal deposit

Legal deposit

Legal deposit is a legal requirement that a person or group submit copies of their publications to a repository, usually a library. The requirement is mostly limited to books and periodicals. The number of copies varies and can range from one to 19 . Typically, the national library is one of the...

libraries in the UK. Although there is no such law in place for digital maps, the Ordnance Survey makes annual 'snapshots' of the data and voluntarily deposits with the legal deposit libraries:
The data, like any other, is susceptible to all the problems of computer data storage and digital preservation

Digital preservation

Digital preservation is the set of processes, activities and management of digital information over time to ensure its long term accessibility. The goal of digital preservation is to preserve materials resulting from digital reformatting, and particularly information that is born-digital with no...

, for example: data corruption; the question of how often to take snapshots of the data (i.e. should every edit be recorded?); access to old versions of the data; practicable access to old versions of the data (after format changes, will new software be able to read old data?).

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.